1. Field of the Invention
The present invention relates to the destruction of organic waste using an integrated system of hydrolysis and direct chemical oxidation with peroxydisulfate.
2. Description of Related Art
Destruction of organic waste through conventional thermal techniques, such as incineration, often encounters regulatory or political hurdles, especially when the waste streams contain radionuclides or chlorinated hydrocarbons. Treatment of waste streams containing polychlorinated biphenyls (PCBs) is particularly difficult due to their inertness, persistent biological toxicity, and the possibility of formation of dioxins or furans. When the waste stream is mixed waste, the problem is compounded by the possible volatilization or other release of radionuclides into the environment. For these reasons, alternatives to traditional thermal (&gt;350.degree. C.) organic waste treatment technologies are being developed, e.g., acid digestion and oxidation using multiple catalysts.
One alternative method is mediated electrochemical oxidation (MEO), which is based on the oxidation of organics to carbon dioxide through a series of charge transfer steps involving a mediator. The mediator is a transition metal in a high valency state. The MEO system is limited in the variety of chemical functional groups that can be treated. Furthermore, MEO requires the use of toxic, expensive, and degradable catalysts such as Ag(II) or Co(III). These metals can be lost by precipitation or by entrainment in secondary waste streams, which can then require special and costly disposal.
For certain types of organic waste, such as carbon residues in incinerator ash and mixed waste chlorinated solvents, there are no practical low temperature treatments available. The government and the commercial sector are stockpiling waste until suitable methods can be found to treat or store this waste, and thus there is an urgent need to develop such methods. Waste treatment methods are needed that can be performed at relatively low cost and are more "omnivorous", that is, having the reactivity and oxidizing power to destroy a wide variety of organics.
Many halogenated organic liquids, such as solvents, are difficult to destroy because of their high volatility and limited solubility in water, and a system is needed that circumvents these problems and converts volatile or insoluble wastes into a water soluble, less hazardous, treatable form. In addition, since thermal treatment methods can possibly generate dioxins and furans when treating PCBs, a non-thermal (i.e., &lt;350.degree. C.) technique is desired. Treatment methods should avoid the use of dangerous or toxic gases or highly acidic solutions, and should minimize the secondary waste generated, given the enormous volumes of waste to be destroyed.
It is the object of the present invention to address the problems inherent in the conventional systems and provide a non-thermal, aqueous process that efficiently remediates the organic component of hazardous or mixed wastes while minimizing the economic and environmental costs of a waste treatment system.